April 3, 2007

-- And Now You Don't!

There is an old joke: Q: How many ninjas are hiding in this room? A: As many as want to be.

In a follow-up to our post last October, Now You See It -- -- in which we told you about an amazing breakthrough technology that made objects invisible to electromagnetic (EM) radiation in the microwave part of the spectrum -- we now bring you the next stunning development on the invisibility front.

Scientists now know how to make an object invisible in the "visible light" segment of the EM spectrum... but only for a single wavelength of light. Thus, a person would still be able to see it (though the color might be odd); but to a laser operating at that exact wavelength, the object would be completely invisible:

Researchers using nanotechnology have taken a step toward creating an "optical cloaking" device that could render objects invisible by guiding light around anything placed inside this "cloak."

The Purdue University engineers, following mathematical guidelines devised in 2006 by physicists in the United Kingdom, have created a theoretical design that uses an array of tiny needles radiating outward from a central spoke. The design, which resembles a round hairbrush, would bend light around the object being cloaked. Background objects would be visible but not the object surrounded by the cylindrical array of nano-needles, said Vladimir Shalaev, Purdue's Robert and Anne Burnett Professor of Electrical and Computer Engineering.

The design does, however, have a major limitation: It works only for any single wavelength, and not for the entire frequency range of the visible spectrum, Shalaev said.

"But this is a first design step toward creating an optical cloaking device that might work for all wavelengths of visible light," he said.

To use the metaphor from our previous post, the field would create an "artificial mirage," directing light around the field, like (analogy-shift alert) water flowing around a rock in a stream.

There are two requirements for true invisiblity, as the eggheads explain (but which should be obvious from inspection):

But the light reflected from background objects must somehow be guided around the "invisible" airplane; otherwise, you would see a black, airplane-shaped hole that would make the "invisible" airplane essentially visible.

Requirement number 2 is the hardest to bring about, even in theory; we already have the concept of non-reflective surfaces. But if the technique here can be expanded to channel light from all EM wavelengths simultaneously, from infrared to ultraviolet, then the object inside the field would truly be invisible: You would look right through it as if it weren't there.

But even with the current system, with only one wavelength bent around the field, invisibility can be very practical:

Although the design would work only for one frequency, it still might have applications, such as producing a cloaking system to make soldiers invisible to night-vision goggles.

"Because night-imaging systems detect only a specific wavelength, you could, in theory, design something that cloaks in that narrow band of light," Shalaev said.

Another possible application is to cloak objects from "laser designators" used by the military to illuminate a target, he said.

Making American soldiers disappear from night-vision goggles would truly mean that "we own the night."

We could also cloak tanks, Strykers, and other vehicles, making it virtually impossible for the enemy to see well enough at night to aim at us, even with their own night-vision goggles. And if a target vehicle or building cannot be "seen" by the specific wavelength used by enemy laser-painters, then their missiles will not be able to lock onto the target and hit it.

But with the full-wavelength version, we become like unto the gods of ancient Greece. Imagine... an entire army of ninja Olympians, able to vanish in plain view.

The tiny "bristles" on the "round hairbrush" are really, really tiny... only about 10 nanometers (100 angstroms) in diameter. For comparison, the diameter of a human hair varies between 17,000 and 181,000 nanometers; so each "nanobristle" is about 1/10,000th the diameter of an average human hair.

This itself is very good: The more technologically difficult invisibility is, the greater the advantage to the United States, the United Kingdom, and other nations in the Functioning Core; such advanced, Western nations are the only ones who have active nanotechnology programs. It's hard to envision the Iranians, who cannot even build their own centrifuges to process Uranium, deciding to develop a nanotechnology processing facility.

For invisibility to be useful, those inside the invisibility field need to be able to see out; I'm not sure whether this would work, however. What it actually means to say that you "see" an object -- a tree, perhaps -- is that light reflects off of the tree and into your eyes.

But if light is channeled around you because of the field -- so that objects behind you could be seen as if you were not there -- then wouldn't the light reflected off the tree be likewise guided around you? If so, then you would no more be able to look out than people on the outside would be able to look in.

But let's assume that limitation can be overcome; the military uses would be staggering, turning our already lopsided tactical advantages into an insurmountable gulf that almost satisfies Clarke's Law; as enunciated by science-fiction writer Sir Arthur C. Clarke, the law reads: "Any sufficiently advanced technology is indistinguishable from magic."

But there are other uses for invisibility besides military. Consider the architectural uses: You could design a building where entire blocks of floors (and everything inside them) were invisible, making it appear as though the building consisted of segments literally floating above each other.

Factories could be made invisible, so long as you were outside the field-fence; that would remove eyesores that visually pollute the landscape, while still allowing workers inside the plant to see all the facilities as normal. (Again, we are assuming that those inside can look outside; otherwise, workers might object that they felt as if they were in prison!)

How about movable, removable windows? If you could create an invisible section of any size or shape in a wall, simply by activating the nanobristles in that area, then you could turn windows on when you want them, move them around for aesthetic or other reasons, then turn them off when you retire for the night.

Windows would no longer be "weak points" for a burglar to enter; they would be walls, just like all the other walls. And depending on how well you can fine-tune the field, you might be able to select any of a number of preset "opacity designs," similar to hand-carved window lattices... or even design your own.

There might be some drawbacks; as with any "solution," invisibility is actually a trade-off. For example, you could make a freeway invisible, so that people don't have to look at it. But that also means that a driver might not be able to see how fast or slow the traffic is flowing on the freeway until he enters the on-ramp, making it harder to decide whether to take the freeway or surface streets during rush hour. (But on the whole, I still think the trade-off is a good one.)

Back to the military: It would, of course, be critical that American military personnel and equipment to be able to see all "friendly" equipment in combat -- so that one tank doesn't take a shot at an enemy position, not realizing that there is another American tank or unit of soldiers in the way. This is another hurdle that must be overcome; but again, I always bet on ingenuity and optimism, never on defeatism and technological stasis.

Obviously, we've got a long way to go before we have workable invisibility shields. But "a long way" isn't as long a way today as it was 50 years ago, ten years ago, or even last Tuesday. Not only is technology advancing, but the pace of change itself is also advancing. That means that every year, there are more technological innovations and breakthroughs than in any previous year. In the long run, technology changes everything... even moral and ethical "eternal verities." And society will simply have to adjust to those changes.

Thus, I would never bet the rent money against us developing real "cloaks of invisibility" during the next decade, where it will become critical in winning the war on global jihadism. So keep watching the skies (and this blog); we guarantee to keep you up to date on everything we can't see!

Hatched by Dafydd on this day, April 3, 2007, at the time of 4:34 PM

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Comments

For what it's worth, which is nothing, I should point out that if you do a perfect job of meeting requirement 2 -- routing light around the object to be made invisible -- you will by definition have accomplished requirement 1 -- keeping the object from reflecting light. An object with 360 degree invisibility would be impossible to illuminate since the flashlight in the hands of the guy to the north of the object would be a background light source to the guy to the south.

As for the blindness problem, one solution I like is to pepper the field of activity with "eyes" that simply broadcast what they see all the time. Since the invisible object knows its own location its computers can select the the most convenient views from these external eyes. This assumes the invisible object has a functioning incoming communications link (has solved the visible antenna problem). Since they are broadcasting, the external eyes can be located but locating them would not tell your opponent anything about the location of the invisible object since the external eyes can't see it either. By having large numbers of these external eyes (think bomblets in a cluster bomb) it would become difficult to find and destroy enough of them to blind the invisible object.

And, on topic for a momnet, I'd like to compliment you (again). This post is a great example of why I love reading this site: you cover something here I've not seen at any other blog today, and you do it with the eye of a science fiction writer (though, one obsessed with military matters), so your take on the technology covers not only the military uses but also a whole bunch of imaginative improvements in everyday life. Great read!

For what it's worth, which is nothing, I should point out that if you do a perfect job of meeting requirement 2 -- routing light around the object to be made invisible -- you will by definition have accomplished requirement 1 -- keeping the object from reflecting light.

Well, apart from light sources inside the field itself. Especially for a big object (like a factory), these could be very bright. So you'd want the external structures to have very low reflectivity.

And I don't know whether the nanobristles perfectly redirect light... probably not 100%. So you'd want a tank or a soldier to be as non-reflective as possible as well.

Remember, we don't need invisibility so good that, on a bright, sunny day, you would literally walk right into a Stryker and bump your nose. We need invisibility good enough that a casual glance from a distance would only show empty background.

It's possible that if you knew exactly where to look, you would see a distortion, like a ripple from heat waves.

(Oh yeah, that's another problem... heat emanating from the engine would still produce those heat ripples, with or without an invisibility field; and of course there is exhaust smoke, tracks, shrubbery being compressed in the vehicle's wake, noise, etc. Oh, and an object moving quickly through air would produce a shockwave that could be visible with the right equipment -- allowing you to extrapolate where the object must be. Hey, even the Id Monster from Forbidden Planet left tracks!)

But if a sentry is not particularly alerted, it would be wonderful to be able to invisibly sneak up on a terrorist camp with armor and men, or for an airplane to be able to fly invisibly, making it incredibly difficult for shoulder-fired SAMs to get a lock on the target -- or even for the shooter to see the target.

And it would be very useful for our soldiers and Marines on the ground to be quasi-invisible (anywhere from shadowy to "can't see 'em if they stand still"); it would reduce casualties tremendously.

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